1. Field of Invention
The invention is directed to firing mechanisms for downhole tools and, in particular, to percussion operated firing mechanisms for perforation guns used in opened or cased wellbores.
2. Description of Art
Perforation of opened and cased wellbores using perforation charges is known. In general, perforating a well involves a special gun called a perforation gun that shoots several relatively small holes in the wellbore, e.g., the casing, the cement, or the formation itself, using explosive charges disposed on or within the perforation gun. The holes are formed in the side of the well opposite the producing zone. These communication tunnels or perforations can pierce the casing or liner, the cement around the casing or liner, or the formation. The perforations go through the casing, the cement, or the formation a short distance into the producing well formation. Well formations fluids, which can include oil, water, and gas, flow through these perforations and into the well.
The perforation gun can be run-in the wellbore on wireline or tubing. Firing of the explosives of the perforation gun are generally done by drop-bar, pressure, or by sending electronic signals to the perforation gun which activate an initiator which in turn detonates the perforation charges, such as through the use of detonation cord in communication with each perforation charge. Upon activation of the initiator, the explosives are detonated to shoot the holes in the wellbore.